Magnetic domain wall shift register memory devices with high magnetoresistance ratio structures

ABSTRACT

A device includes a seed layer, a magnetic track layer disposed on the seed layer, an alloy layer disposed on the magnetic track layer, a tunnel barrier layer disposed on the alloy layer, a pinning layer disposed on the tunnel barrier layer, a synthetic antiferromagnetic layer spacer disposed on the pinning layer, a pinned layer disposed on the synthetic antiferromagnetic spacer layer and an antiferromagnetic layer disposed on the pinned layer, and another device includes a seed layer, an antiferromagnetic layer disposed on the seed layer, a pinned layer disposed on the antiferromagnetic layer, a synthetic antiferromagnetic layer spacer disposed on the pinned layer, a pinning layer disposed on the synthetic antiferromagnetic layer spacer, a tunnel barrier layer disposed on the pinning layer, an alloy layer disposed on the tunnel barrier layer and a magnetic track layer disposed on alloy layer.

DOMESTIC PRIORITY

This application is a continuation of and claims priority from U.S.patent application Ser. No. 14/506,798, filed on Oct. 6, 2014, entitled“MAGNETIC DOMAIN WALL SHIFT REGISTER MEMORY DEVICES WITH HIGHMAGNETORESISTANCE RATIO STRUCTURES”, the entire contents of which areincorporated herein by reference.

BACKGROUND

The present invention relates to magnetic domain wall shift registermemory devices, and more specifically, to magnetic domain wall shiftregister memory devices with high magnetoresistance ratio structures andmethods of fabricating the same.

Magnetic domain wall shift register memory devices require sensingelements to read out the signal from the magnetic track. Currently,there are two major types of sensing elements that are implemented. Onesensing type is a conductive wire that directly contacts with the trackand reads the signal by an anomalous Hall Effect. Another sensing typeis a magnetic tunnel junction (MTJ) disposed on top or at the bottom ofthe track, and reads the tunnel magnetoresistance (TMR). The signal fromthe anomalous Hall Effect is much smaller than that from MTJ. As such,the MTJ is a promising sensing element for reading out the signal fromthe magnetic track. As the MTJ is applied as a reader, the TMR ratio isa key factor in reading the signal. The TMR ratio of the MTJ is usuallylow when permalloy is used as the magnetic track. One can increase theTMR by thickening an MgO (magnesium oxide) layer, but themagnetoresistance dramatically increases. As such, a higher voltage forthe same reading current is required, and generally is unsuitable forreal time readings.

SUMMARY

Exemplary embodiments include a magnetic domain wall shift registermemory device, including a seed layer, a magnetic track layer disposedon the seed layer, an alloy layer disposed on the magnetic track layer,a tunnel barrier layer disposed on the alloy layer, a pinning layerdisposed on the tunnel barrier layer, a synthetic antiferromagneticlayer spacer disposed on the pinning layer, a pinned layer disposed onthe synthetic antiferromagnetic spacer layer and an antiferromagneticlayer disposed on the pinned layer.

Further exemplary embodiments include a magnetic domain wall shiftregister memory device, including a seed layer, an antiferromagneticlayer disposed on the seed layer, a pinned layer disposed on theantiferromagnetic layer, a synthetic antiferromagnetic layer spacerdisposed on the pinned layer, a pinning layer disposed on the syntheticantiferromagnetic layer spacer, a tunnel barrier layer disposed on thepinning layer, an alloy layer disposed on the tunnel barrier layer and amagnetic track layer disposed on alloy layer.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 illustrates a starting structure for an exemplary magnetic domainwall shift register memory device;

FIG. 2 illustrates a flow chart for a method of fabricating an exemplarya magnetic domain wall shift register memory device in accordance withexemplary embodiments;

FIG. 3 illustrates a final structure for an exemplary magnetic domainwall shift register memory device;

FIG. 4 illustrates a starting structure for an exemplary magnetic domainwall shift register memory device;

FIG. 5 illustrates a flow chart for a method of fabricating an exemplarya magnetic domain wall shift register memory device in accordance withexemplary embodiments;

FIG. 6 illustrates a final structure for an exemplary magnetic domainwall shift register memory device;

FIG. 7 illustrates a starting structure for an exemplary magnetic domainwall shift register memory device;

FIG. 8 illustrates a flow chart for a method of fabricating an exemplarya magnetic domain wall shift register memory device in accordance withexemplary embodiments;

FIG. 9 illustrates a final structure for an exemplary magnetic domainwall shift register memory device;

FIG. 10 illustrates a starting structure for an exemplary magneticdomain wall shift register memory device;

FIG. 11 illustrates a flow chart for a method of fabricating anexemplary a magnetic domain wall shift register memory device inaccordance with exemplary embodiments; and

FIG. 12 illustrates a final structure for an exemplary magnetic domainwall shift register memory device.

DETAILED DESCRIPTION

Exemplary embodiments include a magnetic domain wall shift registermemory device with high magnetoresistive ratio structures and methodsfor making thereof. In exemplary embodiments, an effective way toincrease the TMR ratio is to add a cobalt-iron-boron (CoFeB) layerbetween a magnetic track and a magnesium oxide (MgO) barrier of themagnetic domain wall shift register memory device. As such, the systemsand methods described herein, add a CoFeB layer adjacent to the magnetictrack to increase the tunneling probability through the MgO tunnelbarrier and to increase. In exemplary embodiments, the TMR ratio can befurther increased by inserting a spacer layer between magnetic track andthe CoFeB layer. The systems and methods described herein can increasethe TMR ratio a lot with almost no change on magnetoresistance.

FIG. 1 illustrates a starting structure 100 for an exemplary magneticdomain wall shift register memory device. FIG. 2 illustrates a flowchart for a method 200 of fabricating an exemplary a magnetic domainwall shift register memory device in accordance with exemplaryembodiments. At block 205, a seed layer 105 is formed by depositing asuitable metallic substance such as tantalum nitride (TaN), titaniumnitride (TiN) or Ta on a template substance such as silicon nitride(SiN) or silicon oxide (SiO_(x)). At block 210, a magnetic track 110 isdeposited on the seed layer 105. The magnetic track 110 can be anysuitable material such as a permalloy, Fe, Co, nickel (Ni), CoFe or anykind of magnetic alloy. At block 215, a CoFeB alloy layer 115 isdeposited on top of the magnetic track 110. In exemplary embodiments,the CoFeB layer can be any CoFeB structure, including CoFeB|CoFe andCoFeB↑Fe bilayers. At block 220, a tunnel barrier MgO 120 is depositedon the CoFeB alloy layer 115. At block 225, a pinning layer 125 isdeposited on the tunnel barrier MgO 120. At block 230, a syntheticantiferromagnetic (SAF) spacer layer 130 is deposited on the pinninglayer 125. At block 235, a pinned layer 135 is deposited on the SAFspacer layer 130. The pinning layer 125, the SAF spacer layer 120 andthe pinning layer 125 together form SAF layers. In exemplaryembodiments, the pinning layer 125 can be a pure CoFeB layer with Fecontent ranging from 10% to 90%, a pure CoFe layer or a bilayerstructure with CoFeB|Fe, CoFe|CoFeB, or two CoFeB layers with differentcompositions. In exemplary embodiments, the SAF spacer layer 130 can beruthenium (Ru). In exemplary embodiments, the pinned layer 135 can beCoFe or CoFeB. At block 240, an antiferromagnetic layer 140 is depositedon the SAF layers (i.e., on the pinned layer 135. In exemplaryembodiments, the antiferromagnetic layer 140 can be platinum manganese(PtMn) or iridium manganese (IrMn). At block 245, MTJ islands are formedby etching portions of the SAF layers (i.e., the pinning layer 125, theSAF spacer layer 130, and the pinned layer 135) and theantiferromagnetic layer 140. FIG. 3 illustrates a final structure 300for an exemplary magnetic domain wall shift register memory device afteretching at block 245.

FIG. 4 illustrates a starting structure 400 for an exemplary magneticdomain wall shift register memory device. FIG. 5 illustrates a flowchart for a method 500 of fabricating an exemplary a magnetic domainwall shift register memory device in accordance with exemplaryembodiments. At block 505, a seed layer 405 is formed by depositing asuitable metallic substance such as TaN, TiN or Ta on a templatesubstance such as SiN or SiO_(x). At block 510, a magnetic track 410 isdeposited on the seed layer 405. The magnetic track 110 can be anysuitable material such as a permalloy, Fe, Co, Ni, CoFe or any kind ofmagnetic alloy. At block 511, a spacer layer 411 is deposited on top ofmagnetic track 410 to separate the magnetic track 410 from the followingCoFeB alloy layer to be deposited. In exemplary embodiments, the spacerlayer 411 can be Ta, TaN, vanadium (V), chromium (Cr), molybdenum (Mo),tungsten (W) or Fe. At block 515, a CoFeB alloy layer 415 is depositedon top of the spacer layer 411. At block 520, a tunnel barrier MgO 420is deposited on the CoFeB alloy layer 415. At block 525, a pinning layer425 is deposited on the tunnel barrier MgO 420. At block 530, an SAFspacer layer 430 is deposited on the pinning layer 425. At block 535, apinned layer 435 is deposited on the SAF spacer layer 430. The pinninglayer 425, the SAF spacer layer 420 and the pinning layer 425 togetherform SAF layers. In exemplary embodiments, the pinning layer 425 can bea pure CoFeB layer with Fe content ranging from 10% to 90%, a pure CoFelayer or a bilayer structure with CoFeB|Fe, CoFe|CoFeB, or two CoFeBlayers with different compositions. In exemplary embodiments, the SAFspacer layer 430 can be Ru. In exemplary embodiments, the pinned layer435 can be CoFe or CoFeB. At block 540, an antiferromagnetic layer 440is deposited on the SAF layers (i.e., on the pinned layer 435. Inexemplary embodiments, the antiferromagnetic layer 440 can be PtMn orIrMn. At block 545, MTJ islands are formed by etching portions of theSAF layers (i.e., the pinning layer 425, the SAF spacer layer 430, andthe pinned layer 435) and the antiferromagnetic layer 440. FIG. 6illustrates a final structure 600 for an exemplary magnetic domain wallshift register memory device after etching at block 545.

FIG. 7 illustrates a starting structure 700 for an exemplary magneticdomain wall shift register memory device. FIG. 8 illustrates a flowchart for a method 800 of fabricating an exemplary a magnetic domainwall shift register memory device in accordance with exemplaryembodiments. At block 805, a seed layer 705 is formed by depositing asuitable metallic substance such as TaN, TiN or Ta on a templatesubstance such as SiN or SiOx. At block 810, an antiferromagnetic layer740 is deposited on the seed layer 705. In exemplary embodiments, theantiferromagnetic layer 140 can be PtMn or IrMn. At block 815, a pinnedlayer 735 is deposited on the antiferromagnetic layer 740. At block 820,an SAF spacer layer 730 is deposited on the pinned layer 735. At block825, a pinning layer 725 is deposited on the SAF spacer layer 730. Thepinning layer 725, the SAF spacer layer 730 and the pinned layer 735together form SAF layers. In exemplary embodiments, the pinning layer725 can be a pure CoFeB layer with Fe content ranging from 10% to 90%, apure CoFe layer or a bilayer structure with CoFeB|Fe, CoFe|CoFeB, or twoCoFeB layers with different compositions. In exemplary embodiments, theSAF spacer layer 730 can be Ru. In exemplary embodiments, the pinnedlayer 735 can be CoFe or CoFeB. At block 830, a tunnel barrier MgO 720is deposited on the pinning layer 725. At block 835, a CoFeB alloy layer715 is deposited on top of tunnel barrier MgO 720. At block 840, amagnetic track 710 is deposited on the CoFeB alloy layer 715. Themagnetic track 710 can be any suitable material such as a permalloy, Fe,Co, Ni, CoFe or any kind of magnetic alloy. At block 845, MTJ islandsare formed by etching portions of the seed layer 705, the SAF layers(i.e., the pinning layer 725, the SAF spacer layer 730, and the pinnedlayer 735), and the antiferromagnetic layer 140. FIG. 9 illustrates afinal structure 900 for an exemplary magnetic domain wall shift registermemory device after etching at block 845.

FIG. 10 illustrates a starting structure 1000 for an exemplary magneticdomain wall shift register memory device. FIG. 11 illustrates a flowchart for a method 1100 of fabricating an exemplary a magnetic domainwall shift register memory device in accordance with exemplaryembodiments. At block 1105, a seed layer 1005 is formed by depositing asuitable metallic substance such as TaN, TiN or Ta on a templatesubstance such as SiN or SiO_(x). At block 1110, an antiferromagneticlayer 1040 is deposited on the seed layer 1005. In exemplaryembodiments, the antiferromagnetic layer 1040 can be PtMn or IrMn. Atblock 1115, a pinned layer 1035 is deposited on the antiferromagneticlayer 1040. At block 1120, an SAF spacer layer 1030 is deposited on thepinned layer 1035. At block 1125, a pinning layer 1025 is deposited onthe SAF spacer layer 1030. The pinning layer 1025, the SAF spacer layer1030 and the pinned layer 1035 together form SAF layers. In exemplaryembodiments, the pinning layer 1025 can be a pure CoFeB layer with Fecontent ranging from 10% to 90%, a pure CoFe layer or a bilayerstructure with CoFeB|Fe, CoFe|CoFeB, or two CoFeB layers with differentcompositions. In exemplary embodiments, the SAF spacer layer 1030 can beRu. In exemplary embodiments, the pinned layer 1035 can be CoFe orCoFeB. At block 1130, a tunnel barrier MgO 1020 is deposited on thepinning layer 1025. At block 1135, a CoFeB alloy layer 1015 is depositedon top of tunnel barrier MgO 1020. At block 1136, a spacer layer 1011 isdeposited on top of CoFeB alloy layer 1015 to separate the followingmagnetic track from the CoFeB alloy layer 715 to be deposited. Inexemplary embodiments, the spacer layer 1011 can be Ta, TaN, V, Cr, Mo,W or Fe. At block 1140, a magnetic track 1010 is deposited on the CoFeBalloy layer 1015. The magnetic track 1010 can be any suitable materialsuch as a permalloy, Fe, Co, Ni, CoFe or any kind of magnetic alloy. Atblock 1145, MTJ islands are formed by etching portions of the seed layer1005, the SAF layers (i.e., the pinning layer 1025, the SAF spacer layer1030, and the pinned layer 1035), and the antiferromagnetic layer 140.FIG. 12 illustrates a final structure 1200 for an exemplary magneticdomain wall shift register memory device after etching at block 1145.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of onemore other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated

The flow diagrams depicted herein are just one example. There may bemany variations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

While the preferred embodiment to the invention had been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

What is claimed is:
 1. A magnetic domain wall shift register memorydevice, comprising: a magnetic track layer; a pinning layer disposed onthe magnetic track layer; a synthetic antiferromagnetic (SAF) layerspacer disposed on the pinning layer; a pinned layer disposed on the SAFspacer layer; and an antiferromagnetic layer disposed on the pinnedlayer.
 2. The device as claimed in claim 1, wherein the magnetic tracklayer is a magnetic alloy.
 3. The device as claimed in claim 1, whereinthe pinning layer is CoFeB layer.
 4. The device as claimed in claim 3,wherein the CoFeB layer includes a Fe content of about 10% to 90%. 5.The device as claimed in claim 1, wherein the pinned layer is CoFe. 6.The device as claimed in claim 1, wherein the pinned layer is CoFeB. 7.The device as claimed in claim 1, further comprising a spacer layerdisposed between the magnetic track layer and the pinning layer.
 8. Thedevice as claimed in claim 1, further comprising a seed layer arrangedbeneath the magnetic track layer.
 9. The device as claimed in claim 8,wherein the seed layer comprises: a template layer; and a metallic layerdisposed on the template layer.
 10. The device as claimed in claim 1,wherein the antiferromagnetic layer is PtMn.
 11. The device as claimedin claim 1, wherein the antiferromagnetic layer is IrMn.